The present invention relates to clothes washing machines and the like and specifically to a lock assembly for preventing access to the spin basket of such a washer during the spin cycle.
During the spin cycle of a washing machine, water is removed from wet clothes centrifugally by spinning the clothes at high speed in a spin basket. In order to reduce the possibility of injury to the user, the user must be prevented from having access to the spin basket while the spin basket is in motion.
One way of protecting the user from access to the rotating spin basket uses a lid switch on the washing machine to detect an opening of the washing machine lid. When the lid is opened by more than a predetermined amount, the lid switch disconnects power from the motor driving the spin basket and activates a brake to bring the rapidly spinning spin basket to a halt. The brake, which is required because of the large rotational momentum of a loaded spin basket, adds significant expense in the manufacture of the washing machine. Systems using brakes may be impractical for future washing machines using higher speed spin cycles to remove greater amounts of water from the wet clothes.
A second way of protecting the user from access to the rotating spin basket uses an electrically actuated lock for the washing machine lid. The lock holds the lid in a closed position for the duration of the spin cycle and for a period after the spin cycle necessary for the spin basket to coast to a stop. The locking mechanism typically uses a thermally actuated element, such as a bi-metallic strip or a wax motor, to position a locking bolt into engagement with the washing machine lid; the bolt prevents the lid from opening. At the conclusion of the spin cycle, the thermally actuated element begins to cool and after a predetermined cooling period, retracts the locking bolt from the washing machine lid and allows the lid to be raised.
The intrinsic delay in the thermally actuated element (required by its need to cool) prevents the lock from being defeated simply by removing power to the washing machine yet in the event of power loss, the lock can be assured of opening on its own after the fixed period of time.
A disadvantage of the thermally actuated element is that it is hard to accurately control the period during which the lid will be locked, the time being affected both by manufacturing tolerance and variations in the temperature of the environment of the washing machine. Further, such a mechanism is difficult to integrate with more sophisticated locking logic, such as systems which operate to reduce the likelihood of child entrapment or misuse of the washing machine. What is needed is an electromechanical locking system that provides the benefits of the thermally actuated element without its disadvantages.
The present invention provides an electromagnetic lid locking mechanism that can release the lid rapidly after a precise interval of time regardless of power failures and which is resistant to being defeated by unplugging the washing machine. The stopping of the spin basket is inferred from the passage of a time interval selected to be longer than a coasting period of the washing machine spin basket. The electromagnetic lid locking mechanism is stable in either the locked or unlocked position when power is removed and hence the lock cannot be defeated by removing power from the washing machine. The circuitry driving the electromagnetic lid locking mechanism monitors and stores electrical power to ensure that the lid may be unlocked at the conclusion of the spin cycle, even if power is lost, reducing the possibility of the lid remaining locked when power fails. The same components and circuitry may be used to provide at small additional cost, a xe2x80x9clock-outxe2x80x9d of the spin cycle in situations where a child might intentionally or unintentionally enter the spin basket after the spin cycle has been initiated while the lid is open.
Specifically, the present invention provides a lid locking assembly having a bistable electromagnetic lid locking mechanism that in a locked state, holds the lid closed until an unlock signal is received and in an unlocked state allows the lid to be freely opened until a lock signal is received, where the unlock and lock signals are power applied to the electromagnetic lid locking mechanism and wherein, absent power applied to the electromagnetic lid locking mechanism, the electromagnetic lid locking mechanism remains in its last state of locked and unlocked. The lid locking assembly further includes a logic circuit having a timer and an energy storage capacitor to provide the unlock signal to the electromagnetic lid locking mechanism a predetermined period of time after the cessation of the washing machine""s spin cycle signal, wherein the storage capacitor provides energy for the unlock signal in the event of loss of external power to the washing machine.
Thus, it is another object of the invention to reduce the possibility of the electromagnetic lid locking mechanism remaining in the locked state when power is removed from the washing machine. The energy used to lock the electromagnetic lid locking mechanism automatically charges a storage capacitor to provide power for the later unlock signal.
It is another object of the invention to provide an electromagnetic lid locking mechanism that responds rapidly to stopping of the spin basket but that cannot be defeated by disconnecting power from the washing machine. During a power failure or after an intentional unplugging of the washing machine, the electromagnetic lid locking mechanism will not automatically release while the spin basket is in motion.
The lid locking assembly may also include a lid switch providing a lid closed signal when the lid is closed. The logic circuitry may receive the lid closed signal and provide power to the motor only when the lid switch indicates that the lid was closed.
Thus, it is yet another object of the invention to reduce the chance of entrapment of a small child if the lid were to close on the child at a time after the spin cycle signal was generated by the machine controls. The present logic circuitry provides this additional feature with a cost effective small addition of parts.
The foregoing and other objects and advantages of the invention will appear in the following description. The description is that of a preferred embodiment which does not necessarily represent the full scope of the invention. The scope of the invention is described by the concluding claims.